Marked As Mine
by bloodamber
Summary: In a world where Downworlder's reign supreme, Shadowhunters have to keep themselves hidden inside one of their last remaining strongholds - the former New York Institute - or face certain extinction. But desperate circumstances force Alexander Lightwood to risk everything to make a deal with the mysterious and feared high warlock, Magnus Bane. (This story is also on AO3)


**Chapter 1**

It was getting dark by the time Alec made his way across town. The bundle in his arms made travel slow and more likely to get caught but he was skilled at avoiding notice and his purpose for being in Downworlder territory was too important to let the risks stop him.

Creeping carefully to the corner of the alleyway he had cut through, Alec looked around. Tapping into his fading hearing rune, he strained his ears for the sounds of anything nearby. When he could hear nothing after a few tense minutes of listening he stepped out and sprinted across the street into the waiting shadows on the other side. Once he was safely out of sight again he looked around for any sign he was in the right place.

The neighborhood he was currently in was home to some of the biggest names in the Downworld. It was an area regarded with much trepidation by the Shadowhunter community due to the sheer number warlocks, werewolves and fair folk that had flocked to the area. He had already felt the slippery sensation of walking through a powerful glamour that he knew would make it all but invisible to the mundanes.

The streets were wide and lined with large trees that in the day time would have made for a beautiful sight but at night took on a sinister edge, their branches casting shadows in which anything could be lurking. The houses themselves were large and varied in outwards appearance, most having been adapted to suit their supernatural inhabitants.

There had been a time, he had been told, when Shadowhunters used to live in such luxury. When their home country of Idris hadn't been an overcrowded stronghold but a place of spectacle. But that had been a long time ago.

The Downworlder uprising had happened years before he was born, a fierce battle between the Shadowhunters and Downworlders, who had united against them and driven the Shadowhunters into near extinction. They had been forced to retreat back to Idris that barely managed to withstand the attacks on its borders, but not without drastic losses - both in people and resources.

His parents, Maryse and Robert Lightwood, had become loyal followers of the charismatic and overzealous Valentine Morgenstern during that time, believing absolutely in his vision and dream of seeing the Downworlders once again brought to their knees and snuffed out. They had followed him from Idris and settled in New York, started raising a family to follow the same indoctrinated ways, wanting to shape him and his younger siblings into perfect little soldiers for Valentine's army.

As their first born, his parents had been all the more hard on him. As long as Alec could remember he had been held to the highest of standards, needing to be faster, stronger and smarter than any other Shadowhunter around him.

Praise was hard earned and failure met with cold disappointment or punishments designed to make him stronger. And despite wanting to make his parents proud Alec always hated the reason he was being trained to fight.

The older he grew and the more he learned, the less he agreed with their mission. He had never felt comfortable with the blind hatred his parents and Valentine seemed to have for the Downworlders. It was no longer about fighting off the demons and protecting the innocent. Instead, Valentine preached of making the world pure again by wiping out all of those with demon blood - including those Downworlders that were innocent victims.

Shaking his head, Alec forced himself to focus. Now was not a time to question his beliefs and dwell on what could have been and so, moving from shadow to shadow, Alec continued to scan the street for his destination.

He only had a brief description of the place he was trying to find, but after half a block he found it, understanding why he had been told _'you_ _will know when you see it'_.

The house of Magnus Bane was massive, taking up took up nearly the entire next block. Distinguishable from its neighbours by the dark brick exterior. A large bay of steps led up to the entranceway that was marked with a golden plaque that had the name BANE engraved on it in large cursive letters.

The door was deep mahogany, intricately carved with archaic symbols that hummed with power the closer he got. The largest symbol – a slitted eye framed by a diamond – started to glow as he reached the top step causing Alec to falter and freeze in alarm. When nothing bad happened in the moments that followed he gathered his courage, shifting the weight in his arms so he could lift the ancient door knocker and let it fall. There was a heavy booming sound that echoed for a few moments before silence fell once again.

Alec stood unsure. As the seconds dragged on he considered knocking again, desperate enough to incur the wrath the Warlock within if it granted him an audience faster. Leaving wasn't an option. Not when what he had come to ask for was too important to give up.

While he waited he looked down at the cause for his desperation - his baby sister, who was tucked against his chest, looking frail and sick.

Izzy had been born when he was only four but he remembered holding her for the first time and feeling a fierce urge to protect. That instinct had never gone away and only become more necessary over the years as she grew up and was subject to the same strict rules and training he was. It was worse seeing her struggle with the same high standards his parents had set for him, seeing how she was forced to give up her childhood to learn how best to fight and kill. Made to hide her emotions because they were seen as a weakness.

She had always been a fiercely independent soul, thinking she could take on everything herself and never one to ask for help, thinking it made her seem weak.

So after getting injured during a mission, hunting down some rogue demons, she had kept the true state of her injury to herself. Instead, approaching Aldertree for help in recovering faster.

Aldertree, one of Valentine's most fanatic followers had found a way to harness the venom from a vampire's bite and turn it into a drug that could mask the pain of almost any wound and increase the healing tenfold. It was also instantly addictive, producing a high, unlike any other drug that led to a withdrawal just as extreme. The longer the drug was used the more dependent the body became on it until the process of withdrawal would kill you.

Izzy had been taking the drug every day for the past two weeks since her injury and although he had noticed her looking more pale and gaunt he had accepted her excuses and deflections. He was ashamed to think it had only been the last few days that he had realized how dire her situation had gotten.

He had only managed to get the whole story from her when she was too sick to hide it anymore. He had been ready to kill Aldertree for the state he had reduced his sister to but Izzy had begged him not to and after realizing just how badly she was suffering he knew she was beyond Shadowhunter help. Aldertree could wait but his sister could not.

So in days that followed he kept his ear to the ground and sought out those he knew had made deals with Warlocks in the past. A name that came up more than once was Magnus Bane, argued to be the most powerful Warlock in the city. None that Alec approached had actually dared go to him for help, seeking out lesser warlocks to fix their problems. But Alec knew his sister needed help from the best if she was going to have any hope of surviving.

The sound of the door unlatching pulled Alec from his thoughts and he looked up to find a glowing golden orb floating in front of him. Alec assumed it was his guide to Magnus and stepped forward over the threshold, shivering when he felt a wash of cold engulf his body. Despite his limited knowledge of Warlock magic, he was pretty certain he had walked through a powerful ward of some sort and had to take a breath to fortify himself before continuing forward.

The passageway he was led through was decorated as ostentatiously as he would have expected, deep red wallpaper with accented gold trimming catching the light. Various paintings, statues, and trinkets lined the lushly carpeted passage and he stared around with wide eyes at the sheer amount of wealth on display. It was a far cry from the military style barracks back in the Institute.

Izzy shifted restlessly in his arms, and he pulled his attention from his surroundings to look down at her watching as her face contorted in pain. He was struck once again with how fiercely he loved her. It hurt him to see her so weak and helpless, but if he had any say in the matter it wouldn't be for that much longer.

* * *

Magnus Bane was everything he had expected, and not.

Dressed in nothing by a pair of black silk pants and matching robe with gold trim, he lounged on a large ostentatious throne, his long legs thrown carelessly over one armrest as he slouched against the other.

Judging by his build Alec guessed he would be tall, although not as tall as him. With tanned skin and features that hinted at southeast Asian heritage.

His hair was meticulously styled, every strand positioned in a way that must have been aided by magic - or copious amounts of hair spray. Earrings decorated his ears and heavy rings glittered across his knuckles. Dark khol outlined golden eyes that were slitted like a cat.

"What brings a child of Nephilim to my home?" His voice when he spoke, was deep and faintly accented.

Alec's tongue felt stuck to the roof of his mouth. Now he was here, in front of _the_ Magnus Bane, he was at a loss of words. The cat eyes were unnerving, pinning him where he stood and Bane shifted on the throne, his robe slipped revealing more of his golden brown skin and toned abdomen that was unmarked by a bellybutton. Alec caught himself staring and quickly averted his eyes in embarrassment and discomfort at another reminder of Bane's inhuman status.

"Speak, before I decide to throw you out for wasting my time."

"My sister is sick." Alec blurted out at the threat, his tongue finally unsticking. "She has been taking Yin Fen."

Magnus raised an eyebrow at the mention of the drug, and his eyes lowered to look at Izzy where she was curled in Alec's arms.

"And here I thought the Shadowhunters considered themselves above such things."

"She was injured, and they gave it to help her heal. She didn't know what it would do to her."

"Surely you have your precious angelic runes to heal in such occasions? I fail to see why I should help you."

"Don't you think I already tried those! Nothing worked and she is only getting worse!" Alec shouted before reigning himself in, taking a breath to calm himself. He couldn't afford to lose his temper at his only chance of help.

"I came to make a deal, for you to help her. Please." Magnus regarded him for a long moment and Alec felt panic settle in. If Magnus refused to help he wasn't sure who else he could turn to.

Then, Magnus snapped his fingers and a low ottoman style couch appeared in front of Alec making him jump.

"I will need to examine her."

Alec hesitated at the request before stepping forward to place Izzy on the couch, smoothing her hair back tenderly before steeling himself and stepping back.

Magnus stood from his throne in a single fluid move and sauntered his way over until he was looking down at Izzy. He brought his hands up to hover over her still form and twisted them in complex patterns, golden mist pouring from his palms to hover over Izzy's still form.

Alec had to hold himself back from attacking Magnus out of instinct and pulling his sister to safety. It was a long moment before the magic rose out of Izzy's body and back into Magnus' hands and dissipated.

"Your sister is very lucky to be alive right now."

"Can you help her?" Alec was desperate. Without Magnus' help, Izzy would die.

"I could." Magnus paused then, looking Alec up and down in a way that was entirely predatory. "At a price, of course."

Alec had been expecting this. "Name it."

The warlock smiled at that. "The question is, how much are you willing to give…"

"Anything within my power and possession to give you." Alec proposed, careful to not promise anything that would allow Magnus to force him into an impossible situation.

Magnus lifted his hand to his chin, black painted nails tapping out against his lips as he thought it over. Alec tried not to fidget under the intense scrutiny Mangus gave him, keeping his back straight and holding the warlock's eyes, determined not to show any weakness.

"For her life, I would require yours in return. That sounds fair, don't you think?" Magnus said after a lengthy pause.

Alec balked, swallowing the instinctual refusal as icy dread crawled up his spine and fear settled in the pit of his stomach. He'd heard of the steep prices warlocks would demand for their services but he didn't think Izzy's health would cost his life. He looked down at his baby sister, lying on the couch, looking much too thin and frail and knew that he would do anything to keep her alive, including sacrificing his own.

Having steeled himself he straightened and looked up to once again meet those golden eyes that had been watching him intently.

"I accept your price." Magnus smiled, looking as smug as a cat that got the cream. Alec shuddered, horrified that his death would bring the creature before him so much joy. But he refused to take his words back, plowing forward with his request instead.

"With one condition." Magnus narrowed his eyes and Alec hastened to explain before the warlock could refuse. "I only wish to witness my sister's recovery and see her healthy again. Our agreement is my life for hers. If she dies then any agreement is null and void." He allowed a small amount of satisfaction that he had gotten one up on Bane, certain he wouldn't refuse.

"Clever Nephilim." Magnus praised, sounding more pleased than angry like Alec would have expected. "Very well. I shall grant you three days in which to see your sister through recovery. I will have a guest room prepared for you here."

With a flourish and a puff of yellow smoke, a vial appeared in Mangus's hands, only a few inches tall and filled with a pearly white substance.

"This will purge the contamination of Yin Fen from her body." Mangus sent the vile out to hover in front of him in offering and Alec took the bottle carefully and pocketed it away.

"Do be sure to give her the entire vile. She will need every drop to recover in her current state." Magnus advised, and Alec nodded, grateful in that moment for the help his sister would soon be receiving.

A snap of Magnus' fingers had another glowing orb appeared before him, clearly meant to be his guide. Alec stepped forward to gather his sister back into his arms before following it towards the exit.

He was almost at the door when Magnus' voice rang out again.

"Oh, and Alec," Alec turned to see Mangus wearing self-satisfied smirk, his eyes roving lazily down Alec's body again before coming up to meet his gaze, "I do hope you said your goodbyes before coming."

* * *

_I've had this idea bouncing around in my brain since the end of last year and the final season of Shadowhunters has me filled to the brim with Malec feels so I thought I would channel them into something productive :P I can't promise a regular posting schedule given boring adult responsibilities but I have a rough plan of about 10 chapters with the next couple of chapters mostly written..._

_Please leave a comment and let me know what you think! ︎_


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